The folks at quattro GmbH just couldn’t leave well enough alone. Not content personalizing Audis for finicky customers (Mass Produced, but JUST FOR YOU), it also acts as Audi’s performance tuning division, and will be responsible for the development and manufacture of the company’s R8 mid-engined sports car in 2008. “quattro GmbH began individualizing A8s in 1995, and became an independent vehicle manufacturer in 1996,” says Thomas Riffel, director, Export Sales, quattro GmbH. “As such, it is responsible not only for the upcoming R8, but also for the RS4, a 420-hp version of Audi’s entry-level A4 sedan.” Audi plans to sell approximately 1,000 RS4s in North America per year, or about 1,500 to 2,000 total before the next generation vehicle is launched. On sale in Europe since November 2005, the total production run for the RS4 could exceed 12,000 units.

“Only the roof and doors are shared with the volume A4 sedan,” says Christian Bokich, manager, A3/A4 Product Planning, Audi of America. Even the 4.2-liter V8, which carries its cam drives on the back of the block so it can fit under the A4’s hood, shares very little with the more pedestrian 350-hp variant used in the rest of Audi’s lineup. “The heads, the type of alloy used in the block, the crankshaft, and other items have been rethought and/or redone for the RS4,” says Bokich. With an 8,250-rpm rev limit, direct injection, a 12.5:1 compression ratio, and 100-hp per liter, the V8 is not your normal Audi engine. It is specially built in Audi’s Gyor, Hungary, plant and shipped to Ingolstadt, Germany, for installation at quattro GmbH’s assembly center.

This facility takes factory-fresh A4s from the assembly line and turns it into an RS4. However, not everything is done in the quattro plant. The Dynamic Ride Control—it interconnects the dampers diagonals to reduce pitch and roll—is fit on the normal A4 line, but filled and tuned when it gets to the quattro facility. The system doesn’t employ any electronics. “It’s true that we do a lot of hand assembly on the car—about 20 hours of it—but there are some things where it is much less expensive and easier to do at the main assembly plant,” says Bokich. To do otherwise, he says, would make all A4s more expensive.

With a base price of $66,000—which doesn’t include the mandatory gas guzzler tax ($2,100) or destination charge ($720)—the RS4 isn’t exactly cheap. This is a nearly $20,000 premium over the higher volume S4 model, which is powered by the 340-hp version of the 4.2-liter V8. Compared to a standard A4 the RS4 is 1.2-in. lower, and the front and rear tracks are 1.5-in. and 1.9-in. wider, respectively. The front brakes are 14.4-in. discs gripped by eight-piston fixed calipers that actuate a total of four pads, while the rears sport 12.8-in. discs with single-piston calipers. They must bring 3,957 lb.—distributed 52/48 front/rear—to a halt in the form of a car capable of traveling from 0-60 mph in 4.8 sec. and electronically governed to a 155 mph top speed. Not surprisingly, two of the five NACA ducts on the front belly pan are dedicated to bringing cool air to the front brakes.—CAS